Thank you for the question.
At common law, the landlord is committing a trespass. Damages
for trespass include any actual damage to land, plus damages for the invasion of the possessor's property rights
. This can include punitive damages.
The problem with all of this is that a trespass action does not permit prevailing party attorney's fees. So, if you sue in circuit rather than small claims court, your recover could be completely overwhelmed by the cost of your attorney.
ORS 90.322 provides damages in the amount of one month's rent for each unlawful entry. Since small claims provides up to a $10,000 damage recovery, you could actually get a fair amount of money, depending upon the amount of your rent and the number of charges you make against the landlord.
In my view, you may want to contact a local attorney and have a demand letter written. The idea would be to entirely avoid any court action and get sufficient damages to dissuade the landlord from bothering you further. If that doesn't work, then I would seriously consider the small claims route before trying to bring a circuit court action. I just don't think you will be able to amass sufficient damages to make hiring a lawyer and actually suing in circuit court a viable alternative.
Please let me know if I can be of further assistance.